The present invention relates to the fabrication of gas turbine engine components and the like, and more particularly, to a novel method for making a gas turbine engine component or the like with a textured surface to improve lubrication distribution between components with interacting or contacting surfaces.
The texture or pattern in the surface of a finished component is of importance if that surface is in contact with or otherwise interacts with the surface of another component. Tribological studies have shown that the wear performance of surfaces are a function of their surface texture or roughness. Under conditions of restricted lubrication, micro-pores can be formed in a surface to act as tiny lubrication reservoirs, or the surface may be specifically patterned to promote lubricant distribution. Surfaces having such micro-pores have been found to out perform conventional smooth finished surfaces; the useful lives of these components have increased relative to the lives of conventional smooth surface components.
Conventional methods for texturing or patterning a surface, used in heavy industry, such as gas turbine engine manufacturing, Basically include mechanical processes, such as grit blasting, honing, grinding and the like. Each of these methods involves contacting a surface with an abrasive medium; these methods typically are not easily controlled for very precise surface patterning, and would not generally be employed where a particular pattern is desired to promote lubricant distribution across the surface of a finished component. Conventional surface texturing operations can also introduce undesirable deformation or other damage into the surface or substrate; the abrasive material may become embedded in some parent materials or otherwise leave behind particulate contaminants or residue which will require an additional process step to clean the surface and remove any contaminants or residue.
Precision patterning of surfaces may become even more critical as nonmetallic composite materials, such as PMR-15 (a glass or carbon fiber composite with an amide resin), find greater application in devices subjected to high stress and heat, such as the components of a gas turbine engine or the like. Conventional surface patterning methods are not applicable to these composite-type materials for the same reasons previously discussed.
The use of excimer lasers (ultra-violet lasers) for material processing, such as micro-machining and deposition of metallic and insulator films is described in marketing and technical literature published by LAMBDA PHYSIK GmbH, a leading manufacturer of excimer lasers, whose address is Hans-Bockler-Str. 12, D-3400, Gottingen, Federal Republic of Germany, and in U.S. Pat. Nos. 4,617,085; 4,756,785; 4,720,621; 4,368,080; 4,328,410; 4,219,721; and 4,128,752. None of these documents recognize the specific problems, as mentioned hereinabove, associated with patterning or texturing the surface of a gas turbine engine component, and in particular a component made of a composite material such as PMR-15, to improve lubricant distribution between interacting gas turbine engine components during engine operation.
A related invention, disclosed in co-pending patent application Ser. No. 07/614,367, filed Nov. 13, 1990, allowed Sep. 12, 1991, entitled "A METHOD FOR MAKING A GAS TURBINE ENGINE COMPONENT", and assigned to the same assignee as the present invention, discloses a method for making an engine component using an ultraviolet laser to prepare a selected surface portion of an unfinished gas turbine engine component or the like for a subsequent bonding or coating step. This Patent Application is incorporated herein by reference.